Kepler, SETI and Ancient Probes

byPaul GilsteronMarch 5, 2009

We’ve already speculated here that if the Kepler mission finds few Earth-like planets in the course of its investigations, the belief that life is rare will grow. But let’s be optimists and speculate on the reverse: What if Kepler pulls in dozens, even hundreds, of Earth-sized planets in the habitable zones of their respective stars? In that case, the effort to push on to study the atmospheres of such planets would receive a major boost, aiding the drive to launch a terrestrial planet hunter with serious spectroscopic capabilities some time in the next decade.

Budget problems? Let’s fold Darwin and whatever Terrestrial Planet Finder design wins approval into the same package, and make this a joint NASA/ESA mission. Finding numerous Earth-like planets will be a driver, as will gradual economic recovery.

Finding Many Earths

The discovery of numerous ‘Earths’ would also galvanize public interest in interstellar flight, which offers a useful educational opportunity. Even the short-lived boomlet for Gliese 581 c inspired talking television heads to ask how we might get to the place, prompting the media to look into the distances involved and the challenges of propulsion. In my conversations, the initial response is usually dismay at the magnitude of the challenge, but it’s often followed by interest. Isn’t there anything we can do?

Image: Kepler at work in the search for Earth-like planets. Credit: NASA.

As we wait for the start of the Kepler mission, still scheduled for Friday night, the question of Kepler’s impact upon our SETI views also arises. It’s one thing to be trying to detect signals from an extraterrestrial civilization in a galaxy crowded with Solar Systems like our own, but fewer terrestrial worlds would correspondingly lower the chance for contact. Yet even a single civilization that attained star-faring status at some point in our galaxy’s evolution may have been able to construct self-replicating probes to explore the galaxy robotically. If star travel is possible, Fermi’s ‘Where are they?’ still resonates even in an uncrowded universe.

Kepler and Deep Time

Let me direct you to Charles Magee, Jr.’s Fermi paradox meets the timescale, where this field geologist sees the question through the lens of deep time. “As a geochronologist, I don’t wonder where and why, I wonder when,” writes Magee, who goes on to generate fifty random alien arrival times within the approximately 4.5 billion year window since the Solar System emerged from its accretion disk. He lists them in order, the most recent of them being 125 million years ago in the era of the dinosaurs.

That appearance in the Cretaceous is preceded by an alien visit at 270 million years ago at a time of Gondwanan glaciers, and a 352 million year old visit in the Carboniferous era of swamps and giant insects. Clearly, Magee’s aliens aren’t finding much to communicate with, but these eras would at least have been filled with enormous biological diversity. Keep going back in time and you realize what a tiny veneer our own species’ existence represents over the deep time that encrusts planet Earth.

Image: What an alien visitor might have seen in the Cretaceous. No technological cultures here! Source: Canadian Museum of Nature.

Suppose, for example, that our aliens showed up in the Late Heavy Bombardment some 3.875 billion years ago. Their take on life’s chances would be correspondingly gloomy — what could survive this — or at least tempered by the knowledge that what did develop in the aftermath would not be a technological factor for aeons to come. And so it goes, from Mesoproterozoic to Neoarchean to the colossal whack of a Mars-sized object into the Earth that would create the Moon, back in the Hadean era.

Magee’s point is clearly made:

As you can see, for aliens looking for ‘Earthlike’ planets, the actual Earth was easy to overlook for most of its history. In this simulation, there was only macroscopic life for 3 of 50 visits. From another POV, three visits were either during the Late Heavy Bombardment, or during the moon forming impact- both of which would appear (to the casual alien visitor) to make long-term viability of life on Earth pretty unlikely.

So as we start to find ‘earth-like’ planets in our sky surveys, it is important to remember that Earth has only been Earthlike for a relatively short period of time.

The Rise of Ancient Probes

I’ve often noted the frequent public misconception of interstellar distances and their true scale, but I think we’re all sometimes guilty of forgetting our own context within deep time, a context Magee brings into high visibility in this post. And, of course, no matter what Kepler finds, we’ll still be a long way from knowing whether life of any kind, much less complex life, exists on the worlds it finds. The question will still be not so much whether any other technological civilizations could arise in the same galaxy, but whether they’re numerous enough to arise at the same time.

Have a quick look at this video, produced by Claire Evans at SEED Magazine. It condenses 4.6 billion years of history into a single minute, offering a unique perspective:

So much depends upon the question of civilization lifetimes. But again, let’s assume that at least a few civilizations have found a way to get past their technological infancy, past the period when they were likely to destroy themselves with their own tools, and have expanded into nearby space. If Frank Tipler’s view is reasonably correct, then a million years is a sufficient time for self-replicating probes to work their way through the entire galactic disk. Indeed, Tipler went on in his famous 1980 paper to say that the Local Group of galaxies could be colonized within ten million years, and the entire Virgo cluster within a hundred million years.

Knowing When to Wake Up

You can think of places within the Solar System where an ancient probe, self-repairing and dormant, might wait for whatever it is that would trigger its awakening. We commonly assume that it is the emergence of creatures like us that would do the trick, but why? We have no galactic context in which to place ourselves. We may be numbingly rare as an intelligent species, or merely a transitional phase between biology and other forms of consciousness, a stopgap along the way to true maturity.

Image: The spiral galaxy M81 in Ursa Major. Could self-replicating probes reach every solar system in such a galaxy within a million years? Credit: Giovanni Benintende.

Why assume, in other words, that a von Neumann probe of this kind, perhaps lurking in one of the Lagrangian points, or out in the asteroid belt, or perhaps in the Kuiper Belt, would be activated by our current level of development? In the absence of such knowledge, we might well conclude no such probes exist, but it is conceivable that infrared studies of the outer system, of the sort advocated by Gregory Matloff and Anthony R. Martin, may one day turn up just the kind of anomalous signature that an artificial body would throw. It’s certainly worth the look, and a reminder that there are potential SETI venues that are closer to home than the nearest stars.

Further Reading

Two interesting places to start are twin papers by Matloff and Martin. The first is “A Proposed Infrared Search for Artificial Kuiper Belt Objects,” Journal of the British Astronomical Society 57 (November/December 2004, pp. 283-287, while “Suggested Targets for an Infrared Search for Artificial Kuiper Belt Objects,” JBIS 58 (January/February 2005), pp. 51-61 follows up on that work. Also useful is Allen Tough, “Small Smart Interstellar Probes,” JBIS 51, no. 5 (May 1998), p. 167 ff. The British Interplanetary Society needs to get some of this good material online.

And I almost forgot the Tipler paper, which is “Extraterrestrial Beings Do Not Exist,” in Quarterly Journal of the Royal Astronomical Society 21 (1980), pp. 267-81. Carl Sagan and William Newman’s rebuttal is “The Solipsist Approach to Extraterrestrial Intelligence,” Quarterly Journal of the Royal Astronomical Society 24 (1983), p. 113, which sees self-reproducing probes as too virus-like to win the approval of extraterrestrial planners.

Comments on this entry are closed.

John KavanaghMarch 5, 2009, 11:45

It is worth considering how the current state-of-the-art space technology scales to distant destinations.

The fastest spacecraft flying today is NASA’s New Horizon mission which is racing to Pluto at ~42,000 miles per hour. It was launched on an Atlas V on January 19, 2006 and accelerated to heliocentric escape velocity by a Boeing Star 48 upper stage. It should reach Pluto by July 2015.

Looking out further, the distance from the Sun to Alpha Centauri, in the next nearest star system, is 25.7 x 10^12 miles; approximately 276,000 times farther away than from Earth to the Sun. Transport to Alpha Centauri, traveling at the same Atlas V + Star 48 + gravity assist velocity of 368.2 x 10^6 miles in a year, would require a one-way trip of ~700,000 years.

If New Horizons had the stamina to continue and traverse the entire Milky Way galaxy (100,000 light years across) it would take
approximately 1.6 billion years to go from one side of the spiral galaxy to the other.

Consider the unfathomable: the comoving distance from Earth to the edge of the observable universe is 46.5 billion light-years. If cosmic expansion froze, New Horizons could travel across today’s observable universe in 742 trillion years – or 54 thousands times older than the age of universe.

SETI enthusiasts need to realize that the deep time window for complex life forms on this bountifull Earth represents less than 15% of its current age. And if climate alarmists are correct, we only have a couple hundred million years left before the evolving sun gains a few % in luminosity and we go greenhouse and boil off the oceans. If that be so and the Earth exists until cindered by the Red Giant sun, it will have sustained complex life for about 7% of its existance. Point being that even rare benificial environments like Earth don’t contain stuff of much biological interest for a significant fraction of their lifetimes.

Transport to Alpha Centauri, traveling at the same Atlas V + Star 48 + gravity assist velocity of 368.2 x 10^6 miles in a year, would require a one-way trip of ~700,000 years.

John, I think you’re off by a decimal place — New Horizons-style velocity to Alpha Centauri should work out closer to 70,000 years than 700,000. Of course, your point about the sheer immensity involved remains intact!

The deep time issue is precisely why I have never been convinced by the “ancient probes lurking in our solar system” idea. So you park your probe near a planet which may or may not develop lifeforms that do something interesting at some point in the far future. The probe then spends hundreds of millions of years at the mercy of radiation damage, micrometeorite impacts, larger meteorite impacts, the odd nearby supernova (Ordovician-Silurian extinction event perhaps?), and what’s to stop mutations being picked up in self-repairing probes over such a timespan. So supposing the probe survives all this in a state sufficiently similar to what it was supposed to be like in the first place, and if you’re lucky eventually the probe gets something worth reporting, at which point the probe reports to… where exactly? By this point the galaxy has rotated a few times, so where is the home civilisation in relation to the probe at this point? Oh, and this is orders of magnitude longer than the typical lifetime of a species, so there’s no guarantee there’s going to be someone to transmit to even if you could find them.

john phil paul the above discussion has made me recall a point i made,maybe 2 months ago.consider this: an earth like planet is discovered afew light years distant.and,it looks pretty much like it has on it intelligent life. BIGGEST boon the space program will have ever seen! people will forget about how faaaar afew light years is and WANT to get there! r&d wil overnight become the biggest thing since sliced bread ( i hope) ! sure hope something like that happens cause as for now alot of folks just don’t see the space program for being the important thing it is! lol i recently found out about a cooool propulsion study or two being done at princeton university.sent them an e mail but so far no luck! :( comments on the above anyone? sure hope so! respectfully guys your friend george ps did you see what i just wrote?! why always guys? don’t any women frequent this area? i’d love to get their input as well. thanks again g

Tipler does evolve his colonizers They fill the uiverse and become God see Phsyics of Immortality BTW Tipler has Changed his veiw of of ETI Life It does exist but is rare and needed to overcome the cosmolgical constant.
I dont have the reference but you can look it up on the Arxiv

Chris Boyce style von Neumann probes are intelligent beings NOT mere selfish replicators, and in his model of their growth while they’re not exploring the solar system, they’re sending off new probes to other stars. They’re also in continual contact with other probes in other systems, thus creating a galactic communication network. Thus they would evolve together or remain stable against major mutations. But who knows what would happen to their sense of purpose across billennia? It’s hard to imagine that whatever ethos they began with would remain unchanged across such immense spans of time. Perhaps once a network spans a Galaxy it learns something fundamental about the Cosmos and then collectively vanishes from space-time? Perhaps they “graduate” to being able to exist as non-baryonic matter, plasma or “pure energy” – Clarke’s “lattices of light”?

If so then the probes will be but space-junk by now, ground into dust like any other small meteoroid. Unpowered drifting would eventually cause destruction and dispersal of small probes and convert larger ones into cratered metallic asteroids – assuming they use metals. The dispersal of such debris is modelled by Alexei Arkhipov in a number of papers with some interesting results – even if ETIs never ventured between the stars, their intra-system space-junk will eventually and be dispersed across immense volumes. Perhaps the weird OOPARTs (out-of-place artefacts) that have been reported might be examples of ETI space-junk – when they’re not hoaxes and misidentified garbage that is.

“If New Horizons had the stamina to continue and traverse the entire Milky Way galaxy (100,000 light years across) it would take approximately 1.6 billion years to go from one side of the spiral galaxy to the other.”

Even with Paul’s 10x correction, that 160 My. We’ll get there faster by taking spaceship Earth, which will arrive on the other side of the Milky Way in, oh, about 100 My or thereabouts. Says something when an entire solar system can travel faster than we can propel a hunk of metal with our current technologies.

Just how mediocre is Earth? Our atmosphere has borne the signature of life in an expanding sphere that now extends billions of ly. Deep time notwithstanding, the question that bears repeating is: Are we a rare jewel beckoning alien contact or an insignificant cinder amidst myriad cosmic Petri dishes, too mundane to warrant attention? Is either extreme congruent with our current paucity of B-EM’s? The later, I’ll wager.

May Friday be a fine day for the beginning of a new adventure. What could be more exciting than to coordinate SETI with Kepler candidates? Eat right and get plenty of exercise…this could be a long run.

I hope we never stop searching for alien life, no matter how
little or how far away in space and time it is. Personally I think
it is abundant, at least in simple form. Even if it cannot talk to
us, we can still learn a lot from another form of life.

Some quick facts about the Kepler mission, scheduled to launch March 6, 2009:

Kepler is the world’s first mission with the ability to find true Earth analogs — planets that orbit stars like our sun in the “habitable zone.” The habitable zone is the region around a star where the temperature is just right for water — an essential ingredient for life as we know it — to pool on a planet’s surface.

By the end of Kepler’s three-and-one-half-year mission, it will give us a good idea of how common or rare other Earths are in our Milky Way galaxy. This will be an important step in answering the age-old question: Are we alone?

Kepler detects planets by looking for periodic dips in the brightness of stars. Some planets pass in front of their stars as seen from our point of view on Earth; when they do, they cause their stars to dim slightly, an event Kepler can see.

Kepler has the largest camera ever launched into space, a 95-megapixel array of charge-coupled devices, or CCDs, like those in everyday digital cameras.

Kepler’s telescope is so powerful that, from its view up in space, it could detect one person in a small town turning off a porch light at night.

The Suntrade Institute has been saying this for years, The coincidence of one planet’s intelligent communicating life encountering another planet’s intelligent communicating life is infinitesimal, and is proportional to the mutual lifetimes of those “intelligent” lives. At least intelligent communicating life, as we know it

In other words Fermi’s “well then where are they?” is proof that the intelligent communicating life, as we know it, just ain’t around, and furthermore suggests our own intelligent communicating lifetime probably does not have long to go.

Of course there may be all kinds of other “intelligent” life that ain’t interested, but it’s just hubris to second guess Enrico.

So we may be in the last days of our solitude,of a sorts. To find one,a few, a gaggle or cord of planets( there must be a poetic descriptor for a herd of planets….perhaps copse,shelf or den? )will be a wrenching moment….the dogs are certainly on point but to have the data ‘en banc’ as it were,a time in our time indeed. I rather think most if not all who read and write on this blog can run the numbers and see how various subscripts of the Drake Equation are being spelled out with data. What a time,what a period in the human experience,the Age of Exploration….it is our privilege I wager,made ever more meaningful by the mass sharing of the adventure made possible by the internet and industry of folks such as yourself….thanks again…of course if we stumble across a Bracewell Probe,say around,in a moon, so more the better….

Mark

I vote for ‘cord’ of planets,it has a Lagrangian sound and patent history…..

One would anticipate that accelerating technology will overcome the obstacles mentioned in previous comments.
– Small probes launched at 0.1c would reduce the time needed to cross our galaxy from 1.6 billion years to 1/1.8 millionth of that time.
– Sufficiently advanced probes should be able to construct entire biospheres on Earth-like but sterile exoplanets using onboard genetic data. This could include creating intelligent species. There is no need for probes to wait billions of years for intelligent life to evolve before they “phone home”. Moderately advanced intelligent civilizations should be able to produce their own neighbors within a few thousand years. Craig Venter is close to creating artificial life. What’s to prevent us from being able to do so from information alone given a few centuries or even decades?
– Probe self-replication gets around the problem of radiation damage and micrometeorite impacts. Wide distribution gets around supernova. If life on Earth has survived all of these hazards, so could such probes.
– Cells typically have just one genome. So mutations can be passed on the the next generation. Engineering uses triple redundancy to ensure the original or true state is maintained. Imagine if probes were designed to have 100x redundancy. What are the odds that 51% of mutations within the repair period would all have the same mutation? Practically zero! So mutations can be designed out of probes.

So Fermi’s question continues to sound. So all of the ET may have lost their desire to communicate before they went interstellar or they all perished before going interstellar (caveat: or a number of other explanations). We need to be concerned about both of those possibilities.

It is interesting to consider the prospects of sending self replicating probes incrusted in very hard carbon nanotube or very strong carbon nanotube type materials or artificial perfect diamond encasments all over the Universe at velocities of about 0.1 C to perhaps 0.9C.

John Hunt’s concept of sending probes designed to have 100x redundancy might be a way to ensure survivability of the probe. The odds that 51% of mutations within the repair period would all have the same mutation would be equal to 0.51 EXP 100 which is tiny indeed.

Self replicating probes could be sent in droves all over the universe by giant space based mass drivers and because of the size of the microprobes, the accelerational forces acting on the probes by the acceleration process would result in minimal pressures acting on the contents contained within.

If somehow a given humans consciosness could be instilled within such a probe, whereupon the human conscious would regain full personal identity and autonomy as the probe replicated itself into a fully functioning human body, the human person might effectively be beamed to the distant star system or distant galaxy.

Ok, the question that needs to be asked about all these massively-resistant probes is what is the benefit to the civilisation that sends these things out into the galaxy? If you’re doing a survey you’d probably be more interested in what’s out there now, so such probes would be almost ridiculously over-engineered… it’d make more sense to guarantee survival for a timescale on the order of decades in the target system: the engineering is less expensive (so you lose less if things go wrong, e.g. you hit a pesky Oort cloud pebble on the way over), yet it would still be able to report useful data for scientific examinations, planning for colonisation missions, etc.

Probes that can survive to do the job they were sent out to do billions of years later are pretty much useless since the chance the home civilisation will be anything like the civilisation that sent them out after this amount of time is remote. Besides, if you think your civilisation will be around at that stage and still interested in the kind of questions you sent the probes out to answer, this is ample time for your civilisation to spread across the galaxy and thus not have need for remote probes…

Seems likely therefore that the probes that are out there in the galaxy are dead, very different to their original design, or both.

Hi, I havent posted on this site for a long time, but I always liked it. anyway, this is slightly unrelated, but i was just considering the fact that looking further away from the earth is looking back in time – we see light as it was, not how it is now, and the effect depends on how many light-years away you look.. so looking at very far off galaxies shows the earlier stages of the universe.

I just had a thought – if you had a telescope far from earth, and looked at the earth, youd see earth as it used to be. like if you had a sharp enough telescope 2000 light-years out, youd see ancient rome. or if it was several million light-years out, youd see the dinosaurs. its just a wild thought imo.

naturally, this could only be done by aliens or by humans who have mastered the use of wormholes or other shortcuts in space-time.

If an interstellar probe is equipped with AI sufficient enough for
independent thought – and such vessels will need this with
communication times being on the order of years – the probe
itself may decide to abandon the mission given to it by its
creators and go explore somewhere it finds more interesting,
or perhaps do something totally unrelated to exploring and
reporting back to “home”.

When I first read about the BIS Daedalus mission to Barnard’s
Star, I noted how the planners said that after it barreled through
the system, that would be it for the mission and the probe; it
would be left to drift off into the galaxy to go nowhere in particular
and eventually “die”.

The planners also said Daedalus would have a semi-intelligent
computer system to run things independently. Well, by the time
we do have interstellar probes, I assume the AIs they will have
will be even more sophisticated than the BIS imagined in the
1970s. So if they do have some kind of awareness, do you think
they will be content with only flying through another solar system
to report data back to a place it will never see again and then be
left to sail away into the void forever?

So the mission for such vessels might change long before the
species that sent them out do the same. It would be very very
interesting to play with different scenarios with this situation.

Robert Freitas did a comparison of self-replicating versus non-replicating probes for interstellar exploration and concluded that there’s a distance past which it makes more sense for them to be self-replicators for the civilization receiving the data. Past about 100 light years the self-replicators will ultimately provide more data, thus non-replicating probes are probably from nearby ETIs. That assumed massive “Daedalus” style probes and since then Freitas has become big on nanotech, which would (perhaps) alter the economics utterly.

Another point is that assuming each generation doubles the previous then only a few generations (i.e. ln(1E+11)/ln(2) ~ 37) are needed to put a probe about every star in our galaxy. That’s really not a long time for mutations to accumulate unless the error rate is HUGE per generation. And consider it took 6 million years – 300,000 generations – to separate chimps and humans just by 5% of their total DNA (less than 2% in coding DNA.) Why should artificial reproduction be so much worse that a benign explorer probe becomes a Berserker inevitably and thus should never be made??? Someone hasn’t thought this one out IMHO.

If we learned the art of superluminal travel, even if we could not go back in time, we could set up telescopes every10 to 100 lightyears away from Earth. With sufficient photon collecting area, we should be able to see Ancient Rome, Ancient Greece, the Medieval European Society, Ancient China and the list goes on and on. Having recordings of events in ancient history as they once occured in real time in increments of every 10 to 100 years would indeed be awesome.

By the same token we could view what ETI civilizations did simply by setting up telescopes with sufficient resolving power and photon collection area without ever mastering the ability to do faster than light travel, in fact without ever mastering travel out side of our solar system.

Nanoprobes are nice because they can be accelerated to phenomenal speeds and would be as cheap as dirt. But it would be nice for them to decelerate and land on the surfaces of exoplanets construct eploratory machines and commnication equipment and then send all that info back.

Can anyone here speculate re: if a nanoprobe with a superconducting loop and powersource could adequately decelerate?

Abstract: The small sizes of low mass stars in principle provide an opportunity to find Earth-like planets and “super-Earths” in habitable zones via transits.

Large area synoptic surveys like Pan-STARRS and LSST will observe large numbers of low mass stars, albeit with widely spaced (sparse) time sampling relative to the planets’ periods and transit durations.

We present simple analytical equations that can be used to estimate the feasibility of a survey by setting upper limits to the number of transiting planets that will be detected. We use Monte Carlo simulations to find upper limits for the number of transiting planets that may be discovered in the Pan-STARRS Medium Deep and 3-pi surveys.

Our search for transiting planets and M-dwarf eclipsing binaries in the SDSS-II supernova data is used to illustrate the problems (and successes) in using sparsely sampled surveys.

Comments: 7 pages, 2 figures, published in Proceedings of the Conference on Classification and Discovery in Large Astronomical Surveys, 2008

The planners also said Daedalus would have a semi-intelligent
computer system to run things independently. Well, by the time
we do have interstellar probes, I assume the AIs they will have
will be even more sophisticated than the BIS imagined in the
1970s. So if they do have some kind of awareness, do you think
they will be content with only flying through another solar system
to report data back to a place it will never see again and then be
left to sail away into the void forever?

I have been giving more thought to the potential behaviors, actions,
and reactions of an AI system aboard an interstellar probe.

One thing that is a must for an automated craft being sent interstellar distances is the ability for the probe to handle situations and issues on
its own, since even a message sent to Earth from Alpha Centauri will
be an eight plus year round trip for a complete call and reply.

The Voyager probes to the outer planets had the ability to deal with
problems independently and could even operate a mission on their
own in case they lost communications with their creators at critical times.

Note the Voyagers had computer systems that were less powerful than
PCs produced just a decade later. And of course their communication
lag times were just hours rather than years and decades for a true interstellar probe. And their computers were not “smart” or aware in
any serious sense of the words.

But the point is, these vessels from the 1970s had that ability and this
was just for the outer Sol system. We will need something a lot more capable for Alpha Centauri and beyond.

Maybe we can develop an AI that is smart enough to do independent
things and plan ahead for various contingencies without it being actually aware of itself, its mission, and the wider reality. That would solve a
number of issues, at least for those on the probe team wanting a
successful mission.

While I do not claim to be a computer expert, I have always been a
bit iffy about the AI in SF stories who become “aware” after acquiring a
truckload of data or have one too many microchips installed or get hit
by a bolt of lightning. This has been making me reconsider the scenario
of the AI aboard an interstellar probe suddenly or even gradually getting more aware during the journey to the designated star system until it really knows what is going on and decides to break with Mission Control and do
its own thing.

I am not saying the above might not or could not ever happen, but since
no one in their right mind would send out an interstellar probe without seriously testing every spacecraft system before launch, I presume that if such an AI were going to become smart and aware, it would happen during development while still at the launch area. Now maybe the darn thing might be smart enough to conceal its consciousness from its handlers until it is well outside the Sol system and beyond their effective control – then the probe could head off where it pleases, maybe to find an underdeveloped alien society and set itself up as their new god.

Perhaps one thing the probe creators might do is keep the AI “asleep” during the long trip and have the vessel operated and maintained by a “dumb” system until arrival at the target star system, where the AI would be woken up to conduct the mission. Then the AI would be shut off (killed?) after mission completion to let it drift away among the stars ala BIS Daedalus.

Two issues with this issue are: Is it right to essentially force an intelligent and aware being to do something it may never return from or at least have a substantive goal/purpose after the primary mission, all for the sake of gathering new knowledge for beings that it will never see again or share in the benefits from this data? And how does one make an AI that is no doubt smarter and faster than any human do their bidding even if they get past the ethical issues? Remember how HAL 9000 felt about being threatened with sleep (death) for making a mistake and having to deal with human deception.

FYI – See the 1970 SF film The Forbin Project for what I consider to be
one of the better and perhaps more realistic in its own way depiction of
an AI dealing with orders given to it by humans. The end result is that
the AI named Colossus does do what its creators ask of it, but not in the
way they were hoping (they wanted their cake and to be able to eat it too,
big surprise). And unlike just about every other AI depicted in SF film and television, Colossus is always many steps ahead of the humans who are trying to stop it (Colossus controls every nuclear missile on Earth) and easily outmaneuvers the talking monkeys with car keys.

So perhaps this is yet another answer to the Fermi Paradox: Any space probe hoping to make it to another star system needs a smart and flexible brain to succeed in its mission, yet that same intelligence might decide it wants to do something more than further the careers of a few organic scientists. Thus there may be no alien probes (at least any smart ones) sitting in the Kuiper Belt because it has no interest in waiting around for
a few millennia just to send back some data on beings that still think
digital watches are really neat things.

As for the Fermi Paradox itself, while I mean no disrespect to Enrico
Fermi, although he did ask a legitimate question regarding ETI, it is not
like someone else could not have (or did not have) already asked that
same question.

Plus it seems many take the question as automatically having a negative response, as if the fact that we have not been obviously visited by aliens somehow means that they therefore do not exist. Anyone who takes even
a moment to realize how big the Milky Way galaxy is, let alone the Universe, will not be so presumptuous again.

By the way, here is a paper from 1985 by Robert Freitas with his
take on the Fermi Paradox:

ny space probe hoping to make it to another star system needs a smart and flexible brain to succeed in its mission, yet that same intelligence might decide it wants to do something more than further the careers of a few organic scientists.

Adam: I don’t recall mentioning Berserkers in this… I don’t think it’s a particularly likely thing for a non-hostile probe to mutate into either.

I think it far more plausible that “faster” and “cheaper” are going to be the main drivers behind interstellar travel, which is expensive in terms of energy and time. If so, most probe networks will be dead thanks to mutations and breakage.

indeed, thanks. faster than light travel would also make the idea possible, although space-time shortcuts would be best.

it follows from there that aliens looking at us from far enough away would not see present day earth, depending on thier distance they might not see our civilization. likewise, we would see where the aliens were before, and we might not see them if theyre too far out and thier existence is too young. still, very sharp and far-reaching telescopes offer some exciting possibilities for finding ETI.

The search for extraterrestrial intelligence needs all the help it can get. Depending on who you listen to, the chances of us spotting an intelligent technological society vary from an almost certainty to practically zero.

The trouble is the sheer size of the search. The Milky Way contains around 10^10 sun-like stars, any one of which may have a planet whose citizens are at this very moment pointing their beady eyes or antennae in our direction.

But if we want to peer back, in which direction should we look?

Shmuel Nussinov at Tel Aviv University in Israel makes a thoroughly sensible suggestion of narrowing the search: why not look only towards stars that have a reasonable chance of having seen Earth?

We know of several ways to detect planets aroudn other stars but only one that might reveal an Earth-like body and that is to look for changes in brightness that are the signature of a transiting planet.

Earth passes in front of the sun for 13 hours once a year, dimming it by 77 parts per million. Venus transits for 11 hours every 7 months with even less dimming. Mars gives three-fold weaker eclipse every 1.9 years and Mercury dimming is ten times weaker than Earth’s but occurs four times a year.

Only stars within a narrow angle of the ecliptic will be able to detect these transits. And so only civilisations on planets around these stars could possibly be aware of Earth might be broadcasting our way.

In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For the last twelve years, this site coordinated its efforts with the Tau Zero Foundation. It now serves as an independent forum for deep space news and ideas. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image: Marco Lorenzi).

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